Technical Abstract:
The effects of fish oils, containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), on cyclooxygenase activity and eicosanoid production have been extensively studied, but data on the effects of dietary DHA alone on the synthesis of thromboxane (TXA2) and prostacyclin (PGI2) in the human are lacking. We measured the effect of replacing 2% of fcalories from oleic acid with an equivalent amount from DHA on the excretion of 11-dehydrothromboxane B2 (11-DTXB2) and 2,3-dinor-6-oxo- PGF1alpha (PGI2-M). In a longitudinal study, seven healthy men, living in a metabolic unit, were fed a 30% fat reference diet (RD) for 30 days, then an intervention diet (ID) containing 6 g/d of DHA for 90 days. A control group of four subjects remained on the RD for the duration of the study (120 d). Three-day urine pools were collected at the end of each dietary period (around day 30 and day 120) and analyzed for eicosanoid metabolites excretion by GC-ECCI-MS-MS. Mean excretion of 11-DTXB2 was 590 +/- 256 ng/ (SD; n=7) with the RD, and 385 +/- 148 ng/d with the ID, a 35% reduction (p=0.013 by ANOVA including the control group, total n=11, on log transformed data). Production of 11-DTXB2 in the control group was unchanged. Mean excretion of PGI2-M was 229 +/- 73 ng/d (SD; n=7) and 210 +/- 102 ng/d with the RD and ID diet, respectively (a non-significant reduction). Excretion of 11-dehydrothromboxane B3 at day 120 by the men on the ID was not observed. These results indicate that DHA is a much weaker depressor of TXA2 production than EPA and does not suppress PGI2 production.